1. Field of the Invention
THIS INVENTION relates to optical recording materials and to methods of forming optical devices such as diffusers and holograms from such materials. The present specification discloses, inter alia, various systems or mixtures of components which can be provided in the form of an extended layer and which are of such a character that when such an extended layer of such system or mixture is exposed to light or other appropriate radiation, at least some components of the system undergo polymerisation in the areas so exposed, whereby an end product is obtainable, (after any necessary processing steps), which comprises a solid, transparent, or at least light-transmitting sheet or layer characterised by refractive index variations and/or characterised by variations in layer thickness, i.e. by surface relief features. Such systems are useful, for example as holographic recording materials, or in the production of microlens arrays, or of light-diffusing or de-pixelating screens.
2. Description of Related Art
Typically, known systems for the purpose referred to comprise a monomer or monomers capable of undergoing free-radical-initiated polymerisation, a photo-initiator capable of generating free radicals on exposure to radiation of the required wavelengths and a polymeric matrix or binder. Examples of such known systems or mixtures are disclosed in for example U.S. Pat. Nos. 5,470,662 4,963,471, 4,942,112, 3,658,526.